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  • 2801.
    Romer, Rolf L.
    et al.
    Luleå University of Technology. Laboratoire de Géochronologie, Université Paris, Paris, France; Institut de Physique du Globe de Paris, Paris, France.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Perdahl, Jan-Anders
    Luleå University of Technology.
    Geochronology of the Kiruna iron ores and hydrothermal alterations1994In: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 89, no 6, p. 1249-1261Article in journal (Refereed)
    Abstract [en]

    The magnetite-apatite iron ores at Kiruna are hosted in a suite of alkaline volcanic and subvolcanic rocks that was formed in a short time interval of about 20 m.y. between 1900 and 1880 Ma. U-Pb dating of titanite from magnetite-titanite dikes in the footwall of the Luossavaara orebody indicates that the age of the magnetite-apatite ores is 1888 + or - 6 Ma. Titanite-actinolite-calcite assemblages in amygdules are related to the hydrothermal and metasomatic alteration of the wall rocks and the ore. The U-Pb titanite age of the amygdule fill is 1876 + or - 9 Ma. The geographic distribution of the alteration suggests that it is not related to the formation of the iron ores. The youngest major magmatic units in the Kiruna area are 1792 + or - 4 Ma syenites that intruded the supracrustal rocks. The Kiruna area underwent a weak metamorphic overprint during the Caledonian orogeny. Our data are inconsistent with a hydrothermal event at ca. 1.5 Ga as has been suggested earlier.

  • 2802.
    Romer, Rolf L.
    et al.
    Luleå University of Technology. Laboratoire de Géochronologie, Université Paris, Paris, France.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Perdahl, Jan-Anders
    Luleå University of Technology.
    Scapolite: a tracer for the initial lead isotopic composition in sulfide deposits with later additions of radiogenic lead1996In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 31, no 1-2, p. 134-139Article in journal (Refereed)
    Abstract [en]

    The initial lead isotopic composition of metamorphosed and tectonically reworked sulfide deposits is not always preserved, as sulfides easily change their lead isotopic composition through incorporation of lead derived from external fluids or redistribution and recrystallization of the deposit. Sulfide trace-lead and in cases even galena-lead from such deposits may show exceedingly radiogenic lead isotopic compositions. Thus, the initial lead isotopic composition has to be estimated from other minerals. Scapolite, which is a common phase in alteration haloes associated with epigenetic sulfide deposits in northern Sweden, has very low uranium-contents. Therefore, its trace-lead contents could preserve the initial isotopic composition of the ore-forming fluids. As scapolite is more resistant to recrystallization, it is more likely to reflect the original lead isotope signature of the deposit. This is illustrated using scapolite and sulfides from the Pahtohavare Cu-Au deposit in northern Sweden, which is hosted by Palaeoproterozoic mafic tuffites and graphitic schists and was affected by a mild thermal metamorphism during the Caledonian orogeny.

  • 2803.
    Romer, Rolf L.
    et al.
    Luleå University of Technology.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Perdahl, Jan-Anders
    U-Pb age of the Kiruna iron oreand hydrothermal alterations1993In: Abstracts of lectures and posters: 21:a Nordiska geologiska vintermötet 10-13 Januari 1994 Luleå / [ed] Jan-Anders Perdahl, Luleå: Högskolan i Luleå , 1993, p. 173-Conference paper (Other academic)
  • 2804.
    Rona, P.A.
    et al.
    NOAA/AOML, Miami.
    Boström, Kürt
    Stockholm University.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Cronan, D.S.
    Imperial College.
    Jenkins, W.J.
    Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.
    Asymmetric hydrothermal activity and tectonics of the Mid-Atlantic Ridge, 11 degrees to 26 degrees North1984In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 65, no Suppl., p. 974-Article in journal (Other academic)
  • 2805.
    Rona, P.A.
    et al.
    Rutgers University.
    Murton, B.J.
    NOC, European Way, Southampton.
    Boström, K.
    Stockholm University.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Melson, W.G.
    Smithsonian Institution.
    O'Hearn, T.
    Smithsonian Institution.
    Cronan, D.S.
    Royal School of Mines, Imperial College.
    Jenkins, W.J.
    WHOI.
    Carslberg ridge and mid-atlantic ridge: slow-spreading apparent analogs2005In: AGU, Fall Meeting: 5-9 December 2005, San Francisco, California, American Geophysical Union (AGU), 2005Conference paper (Other academic)
    Abstract [en]

    We compare morphology, tectonics, petrology, and hydrothermal activity of a known section of the Mid-Atlantic Ridge (MAR) between the Kane and Atlantis fracture zones (full multi-beam coverage 21N to 31N) to the lesser known Carlsberg Ridge (CR; limited multi-beam coverage plus satellite altimetry). The CR extends from the Owen Fracture Zone (10N) to the Vityaz Fracture Zone (5S) and spreads at half-rates (~1.2-1.8 cm/yr) similar to the MAR: 1) Morphology: Both ridges exhibit distinct segmentation (primarily sinistral) and axial valleys with high floor to crest relief (range 1122-1771 m). Average lengths of segments (CR: 70 km; MAR: 50 km) and crest-to crest width of the axial valley are greater on the CR (40 km) than MAR (23 km). Axial volcanic ridges form the neovolcanic zone on both ridges, typically 2.6 km wide and 213 m high on the CR. Average water depth near segment centers is greater on the MAR (3933 m) than the CR (3564 m). V-shaped patterns oblique to the spreading axis are present on both ridges. 2) Tectonics: Segments on each ridge are predominantly separated by short-offset (<30 km) non-transform discontinuities with longer transform faults generally spaced hundreds of kilometers apart. Bulls-eye Mantle Bouguer Lows (-30 to -50 mgal) are present at centers of spreading segments on both ridges. Metamorphic core complexes of lower crust and upper mantle are present on the MAR section (at fracture zones) and at least at one locality at 58.33E on the CR. 3) Petrology: MORB composition from our 20 stations along the CR fall into the MORB family, with no evidence of hotspot inputs (no excess K or Nb), or extreme fractionation, similar to the MAR section. REE and trace element patterns between 57E and 61E on the CR indicate increasing melt depletion to the northwest, while glasses exhibit a striking systematic increase in MgO (decrease in fractionation) to the northwest and attain among the most primitive composition of any ocean ridge adjacent to the Owen fracture zone (9.93wt percent). Sr, Nd, and Pb isotopic compositions of Indian Ocean MORB are distinct from those of other oceans. They exhibit relatively higher 87Sr/86Sr, and lower 143Nd/144Nd, 207Pb/204Pb and 208Pb/204Pb for a given 206Pb/204Pb invoking mixing and regional-scale contamination of a depleted mantle with a variously designated enriched reservoir (EM1, EM2, DUPAL, etc.). 4) Hydrothermal activity: The MAR section encompasses a low-T hydrothermal field driven by the serpentinization at the Atlantis fracture zone (Lost City at 30N), and three high-temperature fields driven by magmatic heat in the axial valley (Broken Spur 29N, TAG 26N, and Snake Pit 23N). A 70 km-long, 1000 m-thick megaplume was detected in the water column up to 1400 m above the CR axial valley centered at 6.05N, 60.95E in August 2003, the first clear evidence of high-temperature hydrothermal activity on the CR. Further CR hydrothermal evidence includes relict sulfide chimneys at 58E; Mn-oxide coatings on basalts in the axial valley with Fe/Mn ratios at the boundary between hydrogenous and hydrothermal composition with thickness at two stations (1.67S, 67.77E; 5.35S, 68.62E) suggestive of hydrothermal input; and a d3He anomaly (166 per mil) in the water column at one of our stations in April 1979 (5.35S, 68.62E).

  • 2806.
    Rona, P.A.
    et al.
    Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, Miami, FL, USA.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Boström, K.
    Department of Geology, University of Stockholm, Stockholm, Sweden.
    Serpentinized ultramafics and hydrothermal activity at the mid-atlantic ridge crest near 15°N1987In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 92, no B2, p. 1417-1427Article in journal (Refereed)
    Abstract [en]

    The initial occurrence of serpentinized ultramafic rocks at the nontransform intersection of a wall of a rift valley with the wall of a fracture zone is described from a site at the Fifteen Twenty Fracture Zone. The ultramafics crop out in block-faulted terrain on the upper portion of the eastern intersection between the rift valley and fracture zone walls in water depths between 2910 and 3300 m. They comprise cumulate harzburgites, pyroxenites, Iherzolites, and wehrlites, as well as gabbronorites, olivine gabbronorites, gabbropegmatites, and alteration products including serpentinites, bastite serpentinites, and asbestos. The Ti-Zr-Y relations and relatively constant Zr/Ti ratio in basalts recovered with the ultramafic rocks indicate a cogenetic relation from a common magmatic source that has undergone a late stage differentiation in the lower crust. Ongoing hydrothermal activity is indicated by chemical anomalies (δ3He, Mn) in the near-bottom water at the ultramafic outcrop. The upwelling hydrothermal circulation apparently follows crust-penetrating faults that may have controlled the diapiric ascent of the serpentinites and that continue to tap degassing magma and/or mantle. The observations presented indicate that ultramafic cumulates form beneath the rift valley adjacent to long-offset (>100 km) ridge-ridge transform faults, where they are serpentinized by hydrothermal processes within the initial 1 × 106 years of generation of lithosphère at a slow spreading axis. The corners formed by the intersections of the walls of a rift valley with both the transform (RT corner) and the nontransform (RN corner) portions of these fracture zones are principal loci of diapiric emplacement of serpentinized ultramafics.

  • 2807.
    Rona, Peter A.
    et al.
    University of Stockholm.
    Boström, Kurt
    Luleå University of Technology.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Cronan, D.S.
    Imperial College.
    Jenkins, W.J.
    Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.
    Mallette, M.
    Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.
    Hydrothermal mineralization of Mid-Atlantic Ridge 10-27 degrees N1982In: Abstracts with programs (Geological Society of America), ISSN 0016-7592, Vol. 14, no 7, p. 602-Article in journal (Other academic)
  • 2808.
    Rona, Peter A.
    et al.
    NOAA/AOML, Miami.
    Boström, Kurt
    Luleå University of Technology.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Malette, M.
    Smithsonian Institution.
    Melson, W.B.
    Smithsonian Institution.
    Preliminary reconnaissance of the Carlsberg Ridge, northwestern Indian Ocean, for hydrothermal mineralization1981In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, no 45, p. 1-Article in journal (Other academic)
  • 2809.
    Rona, Peter A.
    et al.
    National Oceanic and Atmospheric Administration, Miami.
    Widenfalk, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Boström, Kurt
    Stockholm University.
    Ultramafic rock suite from the rift valley of the Mid-Atlantic Ridge near 15 degrees N1983In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 64, no 45, p. 724-Article in journal (Other academic)
  • 2810.
    Ronchin, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Mattsson, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Hieronymus, Christoph
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Modeling of magma emplacement processes during laccolith growth.2017Conference paper (Other academic)
  • 2811.
    Roos, Åke
    Executive, Länsstyrelser, Länsstyrelsen Gävleborg.
    Detaljstudie av Ljusnanåsen i Rengsjö socken, Gävleborgs län1974Report (Other academic)
    Abstract [sv]

    Berggrunden i Gävleborgs län präglas av tre morfologiska formelement.

    I öster utbreder sig en kustslätt, i söder cirka 30 Km bred, som i norr löper utanför den nuvarande kustlinjen. Denna slätt utgör sannolikt en denudationsyta, ett S.K. peneplan, med låg topografi och med berget rikligt  exponerat mellan sedimenten. Slätten utgör troligen en utlöpare av det subkambriska peneplanet, i söder väl utbildat i bl. a. uppland. Detta peneplan övergår inåt landet i ett höjdområde med bergsmassiv av ganska enhetlig toppkonstans, med vissa toppar överstigande denna nivå. Gränsen mellan slätten i söder och inlandets berg är utbildad som en brant, vars genes är omtvistad. Marin abrasion i kombination med andra morfologiska processer är närmast att förmoda.

    Gnejsgranit med stora fältspatsögon utgör den mest representerade bergarten i länt. Denna bergart uppträder i stora massiv. Ett bälte av kvartsit utgör berggrund vid gränsen till Västernorrland. I länets södra förekommer yngre granit, liksom i Orsa Finnmark i NW. Lågmetamorfa sedimentbergarter och massformiga, ibland skiffriga vulkanbergarter, S. K. Losgrönstenar finns inom samma område. Porfyrer sträcker sig in i flikar i detta område från Dalarna och Härjedalen. Jonisk sandsten finns Orsa Finnmark, liksom i Gävlesänkan i söder. Kambrosilurbergarter finns bara representerade som lösa block i de kvartära avlagringarna. Länets yngsta bergart är Dellenit, en andesit, som finns mellan Dellensjöarna i norr.

    Länets mest representerade jordart är, som i stort landet i övrigt, morän. Dess sammansättning är varierande, vad beträffar blockhalt och matrix. Normalblockig , sandig morän är vanligast. Moränens former är ofta i samstämmighet med den underliggande berggrundens former. Egenformer, i form av ändmoräner .m . ärsparsamt representerade. Isälvsavlagringarna är talrikt, i form av väl markerade åsryggar och deltan i HK-nivå. Under HK-nivå förekommer i åsarna ett antal sandfält med hittills ganska okänd genes. Svallmaterial förekommer ofta i de dalgånga, som i NW riktning drar inåt höglandet. Klapperfält omgärdar de höjder inom kustslätten, som har varit kraftigt exponerade, liksom öarna i det nuvarande kustbandet, Lera och främst mjäla utfyller de lägre liggande delarna av dalgångarna på kustslätten, liksom mindre områden längre in i landet. Mo blir rikligare representerad i sedimenten inom höglandet. Eoliska avlagringar är utbredda främst i södra delen av länet och i höglandet i nordväst. Sedimentslätterna är, med få undantag, torvfattiga.

    Isrörelsen har inom länet övergått från en i söder, kring Gävletrakten, mycket nordlig ritning till , kring Söderhamn, en tydlig avböjning mot NW och W. Räfflor vittnar om flera isrörelseriktningar, inalles tre , en första från WNW, en något senare från NW och en ung, främst representerad i kustzonen, från N och NE . Denna kuströrelse ställs i samband med en förmodad isoscillation i Gävletrakten.

    Den lokala undersökningen tillsammans med övriga resultat ger vid handen, att isen från en nordlig riktning i höjd med Söderhamn, ganska snabbt drar mot väster, samtidigt som iskanten dröjer i norra delen av länet. I höjd med kustslättens övergång i höglandet i W utjämnas denna rörelse, genom att recessionen hejdas i W av över HK uppdykande bergsområden. Isbrämet erhåller nu en jämnare linje i riktning SW-NE, och uppbrytningen tilltar krig kustöarna i NE. Isen ligger kvar i dalarna inåt, och i sprickor mellan bergshöjderna ansamlas stora material mängder. Isavsmältningen med dödisrester inom stora områden. Och med lateral dränering längs sprickor och tunnlar i dalsidorna.

     

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  • 2812.
    Rosa, Diogo
    et al.
    GEUS Geol Survey Denmark & Greenland, Dept Petr & Econ Geol, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark..
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Thrane, Kristine
    GEUS Geol Survey Denmark & Greenland, Dept Petr & Econ Geol, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark..
    Guarnieri, Pierpaolo
    GEUS Geol Survey Denmark & Greenland, Dept Petr & Econ Geol, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark..
    Evidence for Timanian-age basement rocks in North Greenland as documented through U-Pb zircon dating of igneous xenoliths from the Midtkap volcanic centers2016In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 275, p. 394-405Article in journal (Refereed)
    Abstract [en]

    Igneous xenoliths have been identified within the Paleozoic Midtkap volcanic centers of North Greenland that cut through Cambrian-Ordovician deep water trough sedimentary rocks that were subsequently deformed during the south-verging Ellesmerian Orogeny. The xenoliths were characterized geochemically and their zircons dated through the U-Pb technique. This provided ages ranging from 628 to 570 Ma, for xenoliths with granitic and monzonitic compositions, the former apparently older than the latter. These ages, coupled with the geochemical signature compatible with an arc setting, provide evidence for the presence of Timanian like basement in North Greenland. The structural setting suggests that the dated xenoliths belong to an allochthonous unit emplaced during the Caledonian Orogeny and deformed during the Ellesmerian Orogeny. Furthermore, this data provides new evidence for a northwestern extension (through continuation and/or through dispersal) of the late Neoproterozoic Timanide belt, from its type locality, in the Timan-Pechora region in Russia, through Svalbard, into North Greenland, to the Pearya Terrane on Ellesmere Island.

  • 2813. Rosenberg, T. M.
    et al.
    Preusser, Frank
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Fleitmann, D.
    Schwalb, A.
    Penkman, K.
    Schmid, T. W.
    Al-Shanti, M. A.
    Kadi, K.
    Matter, A.
    Humid periods in southern Arabia: Windows of opportunity for modern human dispersal2011In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 39, no 12, p. 1115-1118Article in journal (Refereed)
    Abstract [en]

    Arabia is a key area for the dispersal of anatomically modern humans (AMH, Homo sapiens) out of Africa. Given its modern hostile environment, the question of the timing of dispersal is also a question of climatic conditions. Fresh water and food were crucial factors facilitating AMH expansions into Arabia. By dating relict lake deposits, four periods of lake formation were identified: one during the early Holocene and three during the late Pleistocene centered ca. 80, ca. 100, and ca. 125 ka. Favorable environmental conditions during these periods allowed AMH to migrate across southern Arabia. Between ca. 75 and 10.5 ka, arid conditions prevailed and turned southern Arabia into a natural barrier for human dispersal. Thus, expansion of AMH through the southern corridor into Asia must have taken place before 75 ka, possibly in multiple dispersals.

  • 2814. Rosentau, A.
    et al.
    Klemann, V.
    Bennike, O.
    Steffen, H.
    Wehr, J.
    Latinović, M.
    Bagge, M.
    Ojala, A.
    Berglund, Mikael
    Dalarna University, Verksamhetsstödet.
    Subetto, D.
    A Holocene relative sea-level database for the Baltic Sea2021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 266, article id 107071Article in journal (Refereed)
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  • 2815.
    Rosqvist, Gunhild C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Leng, Melanie J.
    Goslar, Tomasz
    Sloane, Hilary J.
    Bigler, Christian
    Cunningham, Laura
    Dadal, Anna
    Bergman, Jonas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Berntsson, Annika
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jonsson, Christina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 66, p. 22-34Article in journal (Refereed)
    Abstract [en]

    Here we present delta P-18(diatom) data from two high-latitude lakes; one has short residence time and a water isotopic composition (delta O-18(lake)) that fluctuate due to seasonal variations in precipitation and temperature, and the other has delta O-18(lake) that is influenced by longer lake water residence times and evaporation. The delta O-18(diatom) records reveal common responses to precipitation forcing over the past millennium. Relatively wet summers are inferred from delta O-18(diatom) between 1000 and 1080 AD, 1300 and 1440 AD, and during the early 19th century, coincided with periods of high cloud cover inferred from tree-ring carbon isotopes, and other data for high Arctic Oscillation index. While relatively dry summers with increasing influence of winter snow are indicated between 1600 and 1750 AD. The co-response between carbon isotopes in trees and oxygen isotopes in diatoms strengthens the relationship between cloud cover and precipitation and the hypothesis that these changes were the result of significant regional shifts in atmospheric circulation.

  • 2816.
    Rosén, Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Metamorphic Evolution of the Middle Seve Nappe in the Snasahögarna area, Scandinavian Caledonides2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the Snasahögarna area, situated in the central Scandinavian Caledonides, the Middle Seve Nappe Complex mainly consists of pelitic gneisses. Within these garnet and kyanite bearing gneisses the first discovery of metamorphogenic diamond in Sweden has been confirmed by micro raman spectroscopy. The garnet hosted diamond together with associated carbonate and fluid inclusions were deposited by carbon saturated fluids at a pressure exceeding 3.1 GPa. The peak mineral assemblage, Phg Mgs-Sid Grt Ky Jd Rt Coe (Dia), is constrained by microscopic observations and thermodynamic phase equilibrium modeling. Modeled garnet cores equilibrated at c. 750°C and 1.3 GPa together with phengite rims. This early exhumation stage was followed by heating reaching a peak temperature of 880-910°C at 1.05-1.18 GPa. Partial melting following the increased temperature is confirmed by anatectic segregations and microscopic melt related textures in the paragneiss. A fluid restricted environment at the late high temperature stage is inferred from mineral textures, mineral chemistry and low bulk rock loss on ignition. This is in agreement with thermodynamic models.

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    Metamorphic Evolution of the Middle Seve Nappe in the Snasahögarna area, Scandinavian Caledonides
  • 2817.
    Rousku, Sabine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Interaction Between Different Magma Types in the Reyðarártindur Magma Chamber, SE Iceland2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Southeast Iceland exhibits a granophyre pluton called Reyðarártindur, which has never been described in detail before. The Reyðarártindur magma chamber formed 7.30 ± 0.06 Ma ago (Padilla, 2015). Glacial and coastal erosion expose the pluton, and a river cuts through the pluton roof and walls, revealing interaction between different blob-like structures of magma. The formation of magma chambers can take a very long time, it is therefore likely for several different magmas to interact. Incremental formation of different magma batches give rise to mixing and mingling in magma chambers. To understand when the magma mixing was initiated and the mechanisms controlling it, descriptive analysis were made to obtain textural properties of collected rock samples from the field. The purpose for this thesis study was to examine if there is a frequency size and shape distribution of the magma blobs and if the different magma blobs are systematically distributed across the river. Previous studies have inferred conduit locations and magma mixing processes through similar methods. Extensive field studies have provided all samples for this thesis. Five distinct, magma types were described and found to be interacting. There was one ‘host magma’ which the other four different magma types are exposed as ‘blobs’ within. The statistical analysis involved mapping the blob-like structures from photos taken with an Unmanned Aerial System (URA; drone), using the software Inkscape. The data and measurements for the blobs was collected and summarized in ImageJ. The data was then statistically analyzed in Excel, illustrating the frequency of the magma blob’s size and shape distribution in selected parts of the river. The results of the statistical analysis of the magma blobs showed that ~80 % of the blobs existed in a size interval between 0 – 0.1 m2 . This thesis provides a discussion about the implications of the blob distributions for magma chamber recharge and processes within this section of the magma chamber. The shape distribution analysis showed an indication for all the blobs to be more rounded and equant. This suggest that the magma mixing event probably happened at the same time, during a liquid phase.

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  • 2818.
    Rousku, Sabine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Unraveling the Tectonic History of the Aurek Metagabbro within the Seve Nappe Complex, Scandinavian Caledonides2021Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    The Scandinavian Caledonides form a mountain range comprising nappe stacks of numerous far-travelled thrust sheets. The thrust sheets consist of diverse lithologies representing pre- and synorogenic sedimentary and igneous rocks subsequently metamorphosed to various degrees, from the Late Neoproterozoic to Middle Devonian. In particular, (ultra)-high-grade metamorphic rocks have been recorded in the Seve Nappe Complex (SNC), extending >1000 km along strike of the Scandinavian Caledonides. Included in the SNC of northern Sweden is the Vássačorru Igneous Complex (VIC), consisting of bimodal magmatic suites, that formed c. 845 Ma.

    Fieldwork was conducted in the Kebnekaise mountains of northern Sweden, focusing on the high-grade Aurek metagabbro within the VIC of the SNC. Aurek is a key locality representing both initial stages of Iapetus Ocean formation in the Ediacaran and later stage Caledonian subduction affinities, from the collision between Laurentia and Baltica.

    In this study, petrological description, zircon U-Pb geochronology, mineral chemistry analysis, whole rock composition, and thermodynamic modeling was performed. Zircon U-Pb geochronology yielded protolith ages of 609±2.5 Ma, and 614±2.3 Ma, suggesting the Aurek metagabbro to not be part of the VIC, as has previously been described. The age of Aurek can instead be correlated to the Kebnekaise Dyke Swarms at c. 607 Ma, in the Kebnekaise mountains. Whole rock major and trace element data of e.g., Al2O3 (15.0 – 25.0 ppm) versus SiO2 (46.0 – 53.0 ppm), Rb (2.0 – 18.0 ppm), Zr (8.0 – 58.0 ppm) versus Y (2.7 – 18.0 ppm), Th/Yb ratio 0.25 – 2.0 and Nb/Yb ratio 1.30 – 5.14, indicate assimilation of continental crust. These major and trace element signatures show that the protolith of the Aurek metagabbro probably was emplaced in a continental rift setting in the Ediacaran. Semi-quantitative thermodynamic modeling from this study present blueschist to amphibolite facies conditions for the Aurek metagabbro at 11.8 – 12.6 kbar and 480 – 565 oC, confirming the unit experienced subduction, possibly in the Late Cambrian to Early Ordovician. The metamorphic grade and protolith age show similar features to correlative rock sequences in the Tsäkkok Lens, south of Aurek, in Norrbotten.

    Consequently, this study concludes that subduction, exhumation and subsequent deformation for Aurek, probably was equivalent to those of the Tsäkkok Lens, extending the HP affinities of the SNC further north in the Swedish Caledonides.

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  • 2819.
    Routh, Joyanto
    Department of Earth Sciences, University of Roorkee, Roorkee 247667, India.
    Metamorphism and Structural Interpretation of the Zanskar Shear Zone, PJW Himalaya, India1993In: Journal of the Geological Society of India, ISSN 0016-7622, E-ISSN 0974-6889, Vol. 41, no 3, p. 187-198Article in journal (Refereed)
    Abstract [en]

    Herren in 1987, reported normal faults resulted in the telescoping of metamorphic isograds within a 200 meter zone between Sumche Topko to Mulung Topko in the Zanskar Shear Zone NW Himalaya. However petrographic study-of sections obtained from Mulung Topko and surrounding areas (pensila-padarn section) indicate that the rocks belong to the kyanite-sillimanite-starurolite grade only. Extension crenulation cleavage and other shear criteria show an initial NESW movement after which a layer parallel extension occurred and the shear zone developed. Minieralogical assemblage and mapping indicate that the isograds run paralleI to each other before they possibly truncate against the shear zone along the Pensila-Padam section. A probable model has been proposed to explain the features

  • 2820.
    Routh, Joyanto
    et al.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    McDonald, Thomas J.
    Department of Civil Engineering, Texas A&M University, College Station, TX 77843, USA.
    Grossman, Ethan L.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    Sedimentary organic matter sources and depositional environment in the Yegua formation (Brazos County, Texas)1999In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 30, no 11, p. 1437-1453Article in journal (Refereed)
    Abstract [en]

    The complex depositional environment of the Eocene Yegua formation (Brazos County, Texas) can be better understood by integrating organic matter (OM) geochemistry with stratigraphy. Yegua sediments represent parasequences separated by exposure surfaces. Organic petrography and geochemistry (biomarkers, C/N ratios, and carbon isotopes) indicate the presence of both terrestrial and marine OM in transgressive sediments. In contrast, regressive sediments contain only terrestrial OM. These differences relate to contrasting OM sources and depositional styles on the shelf. OM in the sediments is immature and the potential for generating hydrocarbons is poor. The study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations.

  • 2821.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Meyers, Philip A.
    Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063, USA.
    Gustafsson, Örjan
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Baskaran, Mark
    Department of Geology, Wayne State University, Detroit, Michigan 48202, USA.
    Hallberg, Rolf
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Schï¿œldstrï¿œm, Anna
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden2004In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Limnology and Oceanography, Vol. 49, no 5, p. 1560-1569Article in journal (Refereed)
    Abstract [en]

    Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.

  • 2822.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Meyers,, Philip
    Department of Geological Sciences, University of Michigan, Ann Arbor, USA.
    Hjorth, Tomas
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Baskaran, Mark
    Department of Geology, Wayne State University, Detroit, USA.
    Hallberg, Rolf
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Sedimentary geochemical record of recent environmental changes around Lake Middle Marviken, Sweden2007In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 37, no 4, p. 529-545Article in journal (Refereed)
    Abstract [en]

    Geochemical properties of sediments deposited in Lake Middle Marviken over the last 185 years record the impacts of a succession of environmental changes that have occurred in the watershed. Clear-cutting of forests for wood and charcoal and extensive water harnessing to support the local iron mills from 1897 to 1957 is recorded by low C/N ratios, high black carbon, and low TOC and Ntotal accumulation rates. Larger δ13C and δ15N values in sediments deposited during this period imply higher productivity. Fluctuations in Ntotal and Ptotal accumulation rates show that the lake chemistry has varied between P or N-depleted systems that affected the δ15N values. Organic matter in the sediments is predominantly immature terrestrial material. Furthermore, hydrocarbon CPI, TAR, and Paq values conform with the observed geochemical trends, variations in organic matter sources, and changes in the watershed. Accumulation rates of Cd, Pb, Zn, and S remained mostly unchanged throughout the period of mining, but an increase from 1957 to 1980 is most likely associated with air-borne industrial and fossil fuel emissions from regional urbanization. In situ microbial processes, such as iron and manganese reduction, also appear to be important in carbon cycling and in affecting the sediment and water chemistry of this lake.

  • 2823.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Saraswathy, Ambujom
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Collins, Matthew D.
    School of Food Biosciences, University of Reading, Reading, Berkshire, UK.
    Arsenicicoccus bolidensis a novel arsenic reducing actinomycete in contaminated sediments near the Adak mine (northern Sweden): Impact on water chemistry2007In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 379, no 2-3, p. 216-225Article in journal (Refereed)
    Abstract [en]

    Weathering of mine tailings in Adak results in high As concentrations in surface and ground water, sediments, and soil. In spite of the oxic conditions, As-rich surface and ground water samples indicate As(III) species predominantly (up to 83%). Several microorganisms were isolated from the enrichment cultures that were involved in As cycling. Amongst them was Arsenicicoccus bolidensis — a novel gram-positive, facultatively anaerobic, coccus-shaped actinomycete, which actively reduced As(V) to As(III) in aqueous media. A. bolidensis reduced 0.06–0.20 mM day− 1 As(V). As(V) reduction displays a direct correlation between the initial As(V) concentration, growth rate, and biomass yield.

  • 2824.
    Rozada, Lee
    et al.
    Sorbonne Univ, Museum Natl Hist Nat, CNRS, UMR 7207,MNHN,Ctr Rech Paleontol Paris, CP 38,57 Rue Cuvier, F-75231 Paris 05, France..
    Allain, Ronan
    Sorbonne Univ, Museum Natl Hist Nat, CNRS, UMR 7207,MNHN,Ctr Rech Paleontol Paris, CP 38,57 Rue Cuvier, F-75231 Paris 05, France..
    Vullo, Romain
    Univ Rennes, CNRS, UMR 6118, Geosci Rennes, F-35000 Rennes, France..
    Goedert, Jean
    Univ Bordeaux, UMR 5199, Prehist Actuel Culture Environm & Anthropol, Batiment B8, F-33615 Pessac, France..
    Augier, Dominique
    Musee Angouleme, 1 Rue Friedland, F-16000 Angouleme, France..
    Jean, Amandine
    Marchal, Jonathan
    Peyre de Fabregues, Claire
    Yunnan Univ, Inst Palaeontol, Ctr Vertebrate Evolutionary Biol, Kunming 650091, Yunnan, Peoples R China..
    Qvarnström, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Royo-Torres, Rafael
    Univ Zaragoza, Fac Ciencias Sociales & Humanas, Dept Specif Didact, Ciudad Escolar S-N, Teruel 44003, Spain..
    A Lower Cretaceous Lagerstatte from France: a taphonomic overview of the Angeac-Charente vertebrate assemblage2021In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 54, no 2, p. 141-165Article in journal (Refereed)
    Abstract [en]

    Terrestrial ecosystems from the Lower Cretaceous of Europe and bonebeds formed in swampy environments are poorly known. The Berriasian-early Valanginian Angeac-Charente site in France represents an example of both. Nine field campaigns have yielded thousands of fossils of over a hundred taxa, including 16 taxa from vertebrate macroremains with numerous trample and crocodile bite marks; 22 taxa from the abundant vertebrate microremains; >10 vertebrate coprolite morphotypes with plant and vertebrate inclusions; abundant sauropod and stegosaur tracks including some preserved in '4-D'; termite coprolites; mollusc moulds; ostracods and plants, including coniferous wood, cones, leaves and cuticle fragments, charophytes and pollen. The richness, diversity and preservation of the fossils qualify the site as a fossil-Lagerstatte. The site represents a 'snapshot' into a Lower Cretaceous ecosystem. This is supported by REE analyses of biogenic apatite and sediment samples, the fossils being found in a single stratigraphical interval and the record of sedimentological and taphonomic 'frozen scenes'. The Angeac-Charente bonebed is highly diverse, dominated by an ornithomimosaur taxon, and contains both macro- and microfossils. This indicates a complex formation, likely primarily influenced by ecological and biologic processes, but also significant physical processes. These include crocodyliform predation and/or scavenging on turtles, ornithomimosaurs and fishes; probable mass mortality occurrence of an ornithomimosaur herd; possible social behaviour of stegosaurs; limited hydraulic transport of most sauropod bones and intense dinoturbation.

  • 2825.
    Rubinstein, C V
    et al.
    Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CCT CONICETa Mendoza, A. Ruiz Leal s/n, Parque General San Martín, M5502IRA Mendoza, Argentina.
    Vajda, Vivi
    Swedish Museum of Natural History, Department of Paleobiology.
    Middle–Late Ordovician organic-walled phytoplankton from Sweden: diversity and early radiation2023In: Estonian journal of earth sciences, ISSN 1736-4728, E-ISSN 1736-7557, Vol. 72, no 1, p. 158-158Article in journal (Other academic)
    Abstract [en]

    The Borenshult-1 core, drilled in the vicinity of Motala, east of Lake Vättern in south centralSweden, comprises a well-dated and nearly complete succession of marine marly carbonatesdeposited relatively close to land. The 34 core samples analyzed for palynology encompass theupper part of the Darriwilian (Furudal Limestone), the entire Sandbian (Dalby Limestone, theKinnekulle K-bentonite and the lower Skagen Limestone) and the lower part of the Katian (SkagenLimestone). The age of this interval is well-constrained to the late Darriwilian (Stage slice Dw3)–early Katian (Stage slice Ka1), based on conodonts and 206Pb/238U dating of volcanic ashdeposits.

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  • 2826.
    Rubinstein, Claudia V.
    et al.
    IANIGLA, CCT CONICET Mendoza, M5502IRA Mendoza, Argentina.
    Vajda, Vivi
    Swedish Museum of Natural History, Department of Paleobiology.
    High diversity and early radiation of organic-walled phytoplankton in southern Baltica during the Middle-Late Ordovician – evidence from the Borenshult-1 drillcore of southern Sweden2023In: GFF, ISSN 1103-5897, E-ISSN 2000-0863Article in journal (Refereed)
    Abstract [en]

    Highly diverse and well preserved organic-walled phytoplankton were recorded from the Darriwilian–early Katian interval of the Borenshult-1 drillcore. We identified 154 species in 53 genera, and three assemblages were distinguished; Assemblage A of a late Darriwilian age, Assemblage B of a Sandbian age (further subdivided into sub-assemblages B1 and B2), and Assemblage C dated as Katian. Taxa with “Silurian affinities” with previous first appearance datum in the early Silurian, Hirnantian, such as Metaleiofusa and Visbysphaera, are here recorded from the late Darriwilian and Sandbian respectively. These occurrences question the relationship between the appearance of pioneering phytoplankton morphotypes and the Hirnantian glaciation. Other taxa with no pre-Silurian records such as Visbysphaera pirifera subsp. minor, Petaloferidium cazurrum and Dorsennidium cf. D. estrellitae are here present in the Sandbian, where bentonite beds are intercalated. The diversity curve of acritarchs shows similarities with those proposed for the Darriwilian-Katian of Baltica with main differences in the interval with bentonite beds representing an intense volcanic activity. The species Metaleiofusa arcuata Wall is here emended and a new combination is proposed: Petaloferidium cazurrum (Cramer) comb. nov. The genus Fankea is recorded for the first time from Swedish strata, suggesting a dominant high- to middle latitudinal distribution instead of a Perigondwanan distribution. We contend that the location of paleo-southern Sweden contributed to the great diversity seen, since a middle-low latitude provided a suitable habitat with warm, shallow water, rich in nutrients.

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    High diversity and early radiation of organic-walled phytoplankton in southern Baltica during the Middle-Late Ordovician – evidence from the Borenshult-1 drillcore of southern Sweden
  • 2827.
    Rueda, Gemma
    et al.
    Universitat Autònoma de Barcelona.
    Rosell-Melé, Antoni
    Universitat Autònoma de Barcelona.
    Escala, Marina
    Universitat Autònoma de Barcelona.
    Gyllencreutz, Richard
    Universitetet i Bergen.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Comparision of instrumental and GDGT based estimates of sea surface and air temperatures from the Skagerrak2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 2, p. 287-291Article in journal (Refereed)
    Abstract [en]

    Sea surface temperatures (SSTs) and annual mean air temperatures (MATs) are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers (GDGTs) proxies in a marine sediment core from the Skagerrak, off southern Norway. The reconstructed values compare well with annual SSTs and summer air temperatures obtained from composite regional instrumental records. The results provide further confidence in the application of proxies based on GDGTs to estimate past temperatures.

  • 2828. Rune, Sven
    Naturvårdsinventering inom Storsidan, Järvsö, utförd i oktober 1973 av lektor Sven Rune, Gävle.: Textbilagor och inventeringskartor1973Report (Other academic)
    Abstract [sv]

    Den Naturvårdsinventering som här presenteras har utförts sammanlagt under 9 dagar i slutet av september och början av oktober 1973. Arbetet planlades i samråd med lantmäteriets specialenhet nr 2 i Gävleborgs län. Därvid begränsades området till att gälla bygden längs dalgångarna på Storsidan. Arbetet skulle utföras och redovisas som inventeringen inom Lillsidan, daterad 71-11-01. Vid fältarbetet har flygbilder i skala 1:20 000 använts. Avgränsningen av delområden har gjorts på dessa, men redovisningen har skett på karta i skal 1:50 000.

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  • 2829.
    Ruocco, Maria
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Paleomagnetic analyses of continental deposits of the last 3 Ma from Argentina: magnetostratigraphy and fine structures of reversals1990Doctoral thesis, monograph (Other academic)
  • 2830.
    Russell, Richard V.
    Stockholm University.
    Geologic examples of small-scale differentiation phenomena: flecky gneiss, orbiculites and experimental models1972Doctoral thesis, comprehensive summary (Other academic)
  • 2831.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Institute für Geoökologie, Technische Universität Braunschweig, Brunswick, Germany.
    Wavelength dispersive X-ray fluorescence spectroscopy as a fast, non-destructive and cost-effective analytical method for determining the geochemical composition of small loose-powder sediment samples2014In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 52, no 3, p. 265-276Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence spectroscopy (XRF) has been used extensively to analyze many types of environmental samples, including lake sediments. In most cases, however, analyses have required either a relatively large sample mass or sample pretreatment, e.g. lithium borate fusion, and have not taken advantage of the potential of XRF analysis as a non-destructive technique. This paper describes the development of two completely non-destructive calibration methods that use small, i.e. 200- and 500-mg loose-powder sediment samples. Analytical performance of these methods was assessed using ten different certified reference materials and a previously analyzed sediment profile, and for both methods, accuracy and precision were less than +/- 10 % (or a few ppm) for 26 elements (Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, Zr, Sn, Sb, Ba, W and Pb). This shows that quantitative wavelength dispersive X-ray fluorescence analysis, using small loose-powder samples, can be a useful geochemical tool for many paleolimnological applications, especially because lack of pretreatment ensures that samples can be used for further analysis.

  • 2832.
    Rydeblad, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Mineral Constraints on the Source Lithologies at Fogo, Cape Verde.2018Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Variations in major, minor, and trace elements compositions and ratios, as well as isotope ratios are all useful tools in studying the composition of the Earth’s mantle, and heterogeneities present therein. Since the mantle itself doesn’t easily lend itself to study, ocean island basalt (OIBs) are commonly used as a proxy due to compositional differences combined with the range of origination depth, a combination that allows them to represent the heterogeneity of the mantle, sampling everything from the core mantle boundary to the old or recent additions of recycled oceanic crust. Fogo, being one of the most active volcanoes in the world, continuously samples the interior of our planet, and as such is a prime location for studies of mantle geochemistry.

    This study aims to determine the origin of the mantle lithologies present at Fogo. The study is a continuation and extension of the studies conducted by Barker et al. (2014) and Magnusson (2016).

    This study utilises major, minor, and trace element geochemistry in clinopyroxene and olivine phenocrysts, as well as Ni-isotopes from whole rock samples. Using the relative values of Ni, Mn, and trace elements and their ratios in olivine and clinopyroxene phenocrysts we aim to further unravel the mechanics of the creation of ocean islands and provide additional constraints regarding the mechanics of the formation of heterogeneities in the Earth’s mantle. This study will focus on Ni* and Mn* in olivine phenocrysts, trace element composition and ratios of olivine phenocrysts and clinopyroxene phenocrysts, and Ni-isotope data. 

    This study found evidence for both pyroxenite, carbonatite, and carbonated eclogite source lithologies at Fogo. A correlation between La/Sm and δ60Ni was also found, indicating a control on the δ60Ni by source pyroxenite.

    This study suggests a carbonated eclogite origin for the lithologies present at Fogo, which would have hosted the majority of the olivine phenocrysts. The phenocrysts then resided within a separated carbonatite melt fraction that either contaminated or metasomatized a pyroxenite melt where the clinopyroxene phenocrysts nucleated. The melt then evolved to an alkali basalt melt through melt-rock reactions, principally via the dissolution of orthopyroxenes and concomitant precipitation of clinopyroxene and olivine (Zhang, Chen, Jackson & Hofmann 2017).      

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  • 2833.
    Rydeblad, Elin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Structural analysis of the hinge region of the Islay Anticline.2016Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The hinge region of a major anticlinal fold structure in the SW Scottish Highlands was located in the eastern part of the Isle of Islay. The structure plunges gently NNW, with the hinge line measuring 02/026. The hinge region was located by mapping a 2km2 area comprised of deformed Neoproterozoic metasedimentary and metacarbonate rocks, and plotting the measurements on stereograms.

    The data collected was also analysed to attempt to asses evidence of refolding, and it is suggested in this thesis that the area displays evidence of at least one subsequent refolding event.

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  • 2834.
    Rydin, Emil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Malmaeus, Mikael
    Karlsson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Jonsson, Per
    Phosphorus release from coastal Baltic Sea sediments as estimated from sediment profiles2011In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 92, no 1, p. 111-117Article in journal (Refereed)
    Abstract [en]

    We used the decline in total phosphorus (P) concentration with depth in sediment profiles from the North-western Baltic Proper coastal zone to calculate the site-specific amount of sediment P eventually to be released to the water column: The potentially mobile P. P fractionation revealed that iron bound P dominated the potentially mobile P at sites with oxic surface sediment layers. Organic P forms were also a major constituent of the potentially mobile P pool. We determined that 1-7 g P/m(2) were potentially mobile at our sites, and the turnover time of this P pool was considered short, i.e., less than a decade. To determine long-term average P fluxes to and from the surface sediment layer, we first multiplied the constant and relatively low P concentration in deeper sediment layers with the sediment accumulation rate to gain the P burial rate. Then the average total P concentration in settling matter was multiplied with the sediment accumulation rate to estimate the depositional P flux at each site. The difference between the depositional and burial rates represents the long-term average release rate of sediment P and varied between 1.0 and 2.7 g P/m(2) yr among our sites. These rates are at the same order of magnitude as values reported from other areas of the Baltic Sea, and constitute a major source of P to the water column.

  • 2835.
    Rydstern, Nils Olof
    Executive, Länsstyrelser, Länsstyrelsen Gävleborg.
    Utredning rörande grusfyndigheternas värde ur ersättningssynpunkt till stöd för översiktlig grustäktsplanerling inom Gävleborgs län1969Report (Other academic)
    Abstract [sv]

    Länsstyrelsen i Gävleborgs län avser att för den framtida täktplanringen inventera och Klassificera grustillgångarna med hänsyn till deras värde ur b1 a naturvårds-, fornminnes- samt vattenförsörjningssynpunkt . Vid inventeringen skall även utredas fyndigheternas volym, läge och betydelse ur exploateringssynpunkt.

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  • 2836.
    Ryr, Caroline
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Sm-Nd isotopic and geochemical signatures along the Matchless Belt amphibolites, Namibia2013Conference paper (Refereed)
  • 2837.
    Ryttberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Significance of Fracture Patterns in a Rock Mass during Excavation by Blasting in Bandhagen, Sweden2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When excavating a rock wall by blasting, pre-existing structures in the rock has a strong impact on the stability of the wall. For excavation in Bandhagen in Stockholm, the nature and orientation of the pre-existing geological features, namely fractures, were not taken into consideration before excavation begun. Geological field studies were carried out in order to investigate the possibility of a more favorable outcome than in the Bandhagen case. Mapping conducted in March 2015 was focused on fracture distribution and the results showed two sets of open shear fractures with fresh surfaces. The first set of the fractures cross-cuts the wall with a strike of NNW-SSE and dips between 70°±30°. The second set of fractures strikes WSW-ENE and are almost parallel to the wall (which strikes roughly 65° E) with a dip towards it, ranging between 55°±35°. The two set of fractures intersect with an acute angle of around 80° and due to their orientation, and that one of the sets dip towards the free face of the wall, they create an unfavorable fracture pattern that makes the wall, at parts, very instable in regard to rockfall and rockslide. 

    Fractures within the respective sets dip towards opposite cardinal points and making an acute angle of 50° for set 2 and 70° for set 1 fractures within the own set are interpreted to conjugate. In addition, there is a well-developed folded foliation that change in strike from parallel to perpendicular to the excavated wall. The foliation is aligned to the strike of both of the fracture sets. This has enabled fractures to open parallel to the mica-rich layers in the gneiss which further adds to the unfavorable pattern of fractures that creates rhombohedral unstable blocks in the rock mass. Due to the fracture pattern, sliding and rockfall have been frequent and safety measures such as rock bolts and a wire mesh have been installed to increase the security factor for the wall.

    During mapping, a general fracture pattern was possible to deduce from mapping of solely an unexcavated, vegetated part of the area. It became clearer though together with the excavated surface of the wall. Several pre-blast measures could have been preformed to limit rockfall and sliding of rock after excavation. Line-drilling could have been used when blasting near the contour of the wall to decrease the blast-induced fractures by the more effective venting of the excess explosion gas. This could have decreased the closely spaced blast-induced fractures that have been mapped on both the crest and the body of the wall. Another measure would have been to install pre-blast reinforcements on the crest of the wall, which could have prevented at least two large rockfalls that have occurred. 

    If the fracture pattern were known before excavation begun and the aforementioned measures would have been considered, the stability of the wall and the first excavation would undoubtedly have been more successful. A proposal for future open face excavations is to thoroughly assess the geological features to, in a preliminary stage of the planning, eliminate the risk for this outcome to occur in the future. 

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  • 2838.
    Saadati, Mahdi
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Forquin, P.
    Weddfelt, K.
    Larsson, Per Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Hild, Francois
    LMT Cachan, Paris, France.
    Granite rock fragmentation at percussive drilling - experimental and numerical investigation2014In: International Journal for Numerical and Analytical Methods in Geomechanics, ISSN 0363-9061, E-ISSN 1096-9853, Vol. 38, no 8, p. 828-843Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to numerically model the fracture system at percussive drilling. Because of the complex behavior of rock materials, a continuum approach is employed relying upon a plasticity model with yield surface locus as a quadratic function of the mean pressure in the principal stress space coupled with an anisotropic damage model. In particular, Bohus granite rock is investigated, and the material parameters are defined based on previous experiments. This includes different tests such as direct tension and compression, three-point bending, and quasi-oedometric tests to investigate the material behavior at both tension and confined compression stress states. The equation of motion is discretized using a finite element approach, and the explicit time integration method is employed. Edge-on impact tests are performed, and the results are used to validate the numerical model. The percussive drilling problem is then modeled in 3D, and the bit-rock interaction is considered using contact mechanics. The fracture mechanism in the rock and the bit penetration- resisting force response are realistically captured by the numerical model.

  • 2839.
    Saarse, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Heinsalu, A
    Poska, A
    Veski, S
    Rajamae, R
    Palaeoecology and human impact in the vicinity of Lake Kahala, northern Estonia1999In: Environmental and cultural history of the eastern Baltic region, ISSN 0257-8727, Vol. 57, p. 372-403Article in journal (Refereed)
  • 2840.
    Saarse, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Heinsalu, A
    Poska, A
    Veski, S
    Rajamäe, R
    Hiie, S
    Kihno, K
    Martma, T
    Early Holocene shore displacement of the Baltic Sea coast east of Tallinn (N Estonia)1997In: Baltica, Vol. 10, p. 13-24Article in journal (Refereed)
  • 2841.
    Saarse, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Poska, A
    Kaup, E
    Heinsalu, A
    Holocene environmental events in the Viitna area, north Estonia1998In: Proceedings of the Estonian Academy of Sciences, Geology, Vol. 47, no 1, p. 31-44Article in journal (Refereed)
  • 2842.
    Saarse, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Poska, A
    Veski, S
    Spread of Alnus and Picea in Estonia1999In: Proceedings of the Estonian Academy of Sciences, Geology, Vol. 48, no 3, p. 170-186Article in journal (Refereed)
  • 2843.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Abt Geowissensch, Adenauerpl 2, D-33602 Bielefeld, Germany;Hof 9, D-51766 Engelskirchen, Germany.
    Hornung, Jahn J.
    Niedersachs Landesmuseum Hannover, Willy Brandt Allee 5, D-30169 Hannover, Germany.
    Lallensack, Jens N.
    Rheinische Friedrich Wilhelms Univ Bonn, Steinmann Inst Geol Mineral & Palaontol, Nussallee 8, D-53115 Bonn, Germany.
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    First evidence of a large predatory plesiosaurian from the Lower Cretaceous non-marine 'Wealden facies' deposits of northwestern Germany2018In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 42, no 4, p. 501-508Article in journal (Refereed)
    Abstract [en]

    Here, we describe the incomplete mandible of a large-skulled pliosauromorph' plesiosaurian from the Lower Cretaceous (Berriasian) of northwestern Germany. The fossil derives from limnic-brackish Wealden facies' deposits of the Deister Formation (Buckeberg Group), and is preserved as a natural mould in fine-grained sandstone. Examination of the original remains, in conjunction with a three-dimensional photogrammetrically digitized cast', revealed a conspicuous rosette of symphyseal alveoli, which would otherwise typically characterize Early-Middle Jurassic macrophagous plesiosaurians including rhomaleosaurids and the pliosaurid Simolestes. The Deister Formation pliosauromorph' represents the first record of a large-bodied plesiosaurian macrocarnivore from the Wealden-facies' strata of Europe, and thus adds a previously unrecognized trophic level of aquatic apex predators to the Early Cretaceous non-marine ecosystems of Europe.

  • 2844.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Bielefeld, Germany; Hof 9, D-51766 Engelskirchen, Germany.
    Jagt, John W. M.
    Nat Hist Museum, Maastricht, Netherlands.
    Niedzwiedzki, Robert
    Univ Wroclaw, Inst Geol Sci, Wroclaw, Poland.
    Kedzierski, Mariusz
    Jagiellonian Univ, Inst Geol Sci, Krakow, Poland.
    Jagt-Yazykova, Elena A.
    Univ Opole, Lab Palaeobiol, Opole, Poland.
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Turonian marine amniotes from the Opole area in southwest Poland2018In: Cretaceous research (Print), ISSN 0195-6671, E-ISSN 1095-998X, Vol. 84, p. 578-587Article, review/survey (Refereed)
    Abstract [en]

    A few isolated plesiosaurian and mosasauroid squamate teeth were collected from the Opole area in southwest Poland during the late nineteenth century. Calcareous nannofossil analysis of their associated rock matrix indicates an early Turonian age (nannofossil zone UC7; Mytiloides ex gr. labiatus and Inoceramus apicalis inoceramid zones), which is significant because this constitutes a globally enigmatic interval of marine amniote evolution. The Opole plesiosaurian teeth are attributable to polycotylids, but an indeterminate mesopodial was also recovered. They are similar to specimens from the Cenomanian–Turonian in the Saxonian Cretaceous Basin of Germany and the Chalk succession of England, but differ from polycotylid remains found in the coeval Bohemian Cretaceous Basin of the Czech Republic, which are far more robust. The mosasauroid tooth crown from Opole compares favourably with dentary and maxillary teeth of a number of Turonian yaguarasaurines and basal russellosaurines, but in having well-developed carinae and a smooth labial and strongly folded/markedly striated lingual tooth surfaces it can be differentiated from taxa such as Yaguarasaurus columbianus (Colombia), Romeosaurus fumanensis and R. sorbinii (both Italy) and ‘Mosasaurusgracilis (England). However, a single record from the Bohemian Cretaceous Basin may refer to a conspecific form. All this suggests a potential for slight compositional differences between Cenomanian–Turonian marine amniote assemblages across central and northern Europe, although otherwise these regions probably constituted a common faunal belt bordering the Tethys Ocean.

  • 2845. Sachs, Sven
    et al.
    Kear, Benjamin P.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Postcranium of the paradigm elasmosaurid plesiosaurian Libonectes morgani (Welles, 1949)2015In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 152, no 4, p. 694-710Article in journal (Refereed)
    Abstract [en]

    Elasmosauridae constitutes one of the most immediately recognizable plesiosaurian radiations. Their distinctive body plan represents the popular model for Plesiosauria, and is typified by an osteological morphology especially adapted for hyper-elongation of the neck. Nevertheless, many archetypal elasmosaurids are known only from incomplete and/or inadequately documented material, a problem that has contributed to their uncertain intra-clade relationships. A prime example of this is Libonectes morgani from the Upper Cretaceous of Texas, USA, which is frequently presented as an elasmosaurid structural proxy because of its three-dimensionally preserved holotype skull. Perplexingly though, both the taxonomic diagnosis and phylogenetic placement of L. morgani rely primarily upon the cervical vertebrae, together with the pectoral girdle and forelimb, yet most of these elements are now lost and figured only as line drawings. We therefore reviewed the remnant postcranial skeleton of L. morgani first-hand with the objective of clarifying its defining character states. Our observations showed that the existing diagnosis of L. morgani is indeed inadequate. Moreover, the only identifiable autapomorphies occurred within the axial skeleton. This concurred with an examination of character scores used in published plesiosaurian phylogenies, and highlights the persistent significance of postcranial elements for discriminating elasmosaurid taxa.

  • 2846.
    Sachs, Sven
    et al.
    Abt Geowissensch, Nat Kundemuseum Bielefeld, Adenauerpl 2, D-33602 Bielefeld, Germany.;Hof 9, D-51766 Engelskirchen, Germany..
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Redescription of the elasmosaurid plesiosaurian Libonectes atlasense from the Upper Cretaceous of Morocco2017In: Cretaceous research (Print), ISSN 0195-6671, E-ISSN 1095-998X, Vol. 74, p. 205-222Article in journal (Refereed)
    Abstract [en]

    The holotype of Libonectes atlasense is an almost complete skeleton from Upper Cretaceous (mid-Turonian) rocks of the Goulmima area in eastern Morocco. Initial assessment of this specimen in 2005 proposed generic referral based on stratigraphical contemporaneity with Libonectes morgani from the Cenomanian-Turonian of Texas, U.S.A. Nevertheless, relative differences in the profile of the premaxillary-maxillary tooth row, position of the external bony nasal opening, number of teeth and rostrad inclination of the mandibular symphysis, proportions of the axial neural arch, and number of cervical and pectoral vertebrae were used to distinguish between these species. As part of an on-going comparative appraisal of elasmosaurid plesiosaurian osteo-anatomy, we re-examined the type and formally referred material of both L atlasense and L morgani in order to establish species validity, as well as compile a comparative atlas for use in future works. Our inspections revealed that these reportedly distinct species-level fossils are in fact virtually indistinguishable in gross morphology. Indeed, the only substantial difference occurs in relative prominence of the midline keel along the mandibular symphysis, which might be explained by intraspecific variation. Furthermore, our observations permit an amendment to the published generic diagnosis of Libonectes with the confirmation of important states such as the likely presence of a pectoral bar, distocaudad expansion of the humerus, and an epipodial foramen. In addition, novel features include a prominent 'prong-like' ventral midline process on the coracoids, and the development of a median pelvic bar that encloses a central fenestration. The composite remains of L morgani thus constitute one of the most complete elasmosaurid skeletal hypodigms documented worldwide, and evidence a trans-Atlantic distribution for this apparently dispersive species during the early Late Cretaceous.

  • 2847.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Abt Geowissensch, Bielefeld, Germany.
    Lindgren, Johan
    Lund Univ, Dept Geol, Lund, Sweden.
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    A global perspective on Mesozoic marine amniotes2018In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 42, no 4, p. 457-460Article in journal (Other academic)
  • 2848.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Abt Geowissensch, Adenauerpl 2, D-33602 Bielefeld, Germany;Hof 9, D-51766 Engelskirchen, Germany.
    Lindgren, Johan
    Lund Univ, Dept Geol, Solvegatan 12, SE-22362 Lund, Sweden.
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Reassessment of the Styxosaurus snowii (Williston, 1890) holotype specimen and its implications for elasmosaurid plesiosaurian interrelationships2018In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 42, no 4, p. 560-574Article in journal (Refereed)
    Abstract [en]

    The holotype (KUVP 1301) of Styxosaurus snowiione of the earliest described elasmosaurid plesiosauriansconsists of a well-preserved cranium, mandible and articulated sequence of anterior-mid-series cervical vertebrae found in the lowermost Campanian strata of the Smoky Hill Chalk Member in the Niobrara Formation of Kansas, USA. This particular specimen has proven important for recent phylogenies of Elasmosauridae, and is integral to resulting definitions of the subfamily-level clade, Styxosaurinae. Despite this, KUVP 1301 has not been redescribed or figured in detail since its original taxonomic establishment. We, therefore, re-evaluated KUVP 1301 and assessed its phylogenetic implications. Several notable character states are pertinent for diagnosing S. snowii at genus and species level: (1) an anisodont functional dentition comprising enlarged premaxillary and dentary teeth with a pair of maxillary fangs', and elongate posterior-most dentary teeth that overlap the upper tooth row; (2) a prominent dorsomedian crest extending from the tip of the premaxillary rostrum, and expanding into a low mound-like' boss between the external bony nasal openings and orbits; (3) a pronounced convex projection on the posterolateral edge of the squamosals; and (4) platycoelous post-axial cervical vertebral centra that are substantially longer than high, and bear both lateral longitudinal ridges and ventral notches. Character state comparisons with the congeneric subfamily specifier Styxosaurus browni suggest that taxonomic distinction is possible, but equivocal. We, therefore, restrict our definition of Styxosaurus to morphologies observable in KUVP 1301. Furthermore, phylogenetic analysis of our first-hand data returns inconsistent elasmosaurid intra-clade relationships, especially with regard to Styxosaurinae. Consequently, we posit that a more targeted reassessment of Elasmosauridae is necessary to resolve both species-level topologies and higher taxonomy within the group.

  • 2849.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Abt Geowissensch, Adenauerpl 2, D-33602 Bielefeld, Germany..
    Lindgren, Johan
    Lund Univ, Dept Geol, Solvegatan 12, SE-22362 Lund, Sweden..
    Madzia, Daniel
    Polish Acad Sci, Inst Paleobiol, Twarda 51-55, PL-00818 Warsaw, Poland..
    Kear, Benjamin P.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Uppsala University, Music and Museums, Museum of Evolution.
    Cranial osteology of the mid-Cretaceous elasmosaurid Thalassomedon haningtoni from the Western Interior Seaway of North America2021In: Cretaceous research (Print), ISSN 0195-6671, E-ISSN 1095-998X, Vol. 123, article id 104769Article in journal (Refereed)
    Abstract [en]

    Thalassomedon haningtoni is one of the most completely preserved elasmosaurid plesiosaurians described to date. Unlike most other elasmosaurid fossils, both the holotype and a second referred specimen -which were recovered from the middle Cenomanian Graneros Shale in the mid-western USA -are represented by intact skulls with articulated postcranial skeletons. Thalassomedon haningtoni thus constitutes an ideal & lsquo;model elasmosaurid taxon & rsquo; that contributes significant character state data towards resolving contested relationships within the clade. Here, we present a detailed reassessment of the cranial osteology of T. haningtoni with the aim of evaluating its disputed species-level monophyly, together with its broader phylogenetic affinities. We identify several key diagnostic cranial traits including a sharply tapered premaxillary rostrum with a pronounced dorsomedian ridge that extends to the tip of the snout, a proportionately very small and rounded external bony nasal opening, and an anisodont functional dentition that incorporates a pair of enlarged & lsquo;fangs & rsquo; in the second maxillary tooth position. Our phylogenetic analyses using first-hand scores unequivocally support classification of the Graneros Shale specimens as conspecific. Furthermore, consistent nesting with other North American elasmosaurid taxa suggests that T. haningtoni could evidence successive lineage divergences that took place within the Western Interior Seaway during the middle to latest Cretaceous. (c) 2021 Elsevier Ltd. All rights reserved.

  • 2850.
    Sachs, Sven
    et al.
    Nat Kunde Museum Bielefeld, Abt Geowissensch, Adenauerpl 2, D-33602 Bielefeld, Germany.;Hof 9, D-51766 Engelskirchen, Germany..
    Madzia, Daniel
    Polish Acad Sci, Inst Paleobiol, Twarda 51-55, PL-00818 Warsaw, Poland..
    Püttmann, Tobias
    Geol Survey North Rhine Westphalia, De Greiff Str 195, D-47803 Krefeld, Germany..
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany2020In: Cretaceous research (Print), ISSN 0195-6671, E-ISSN 1095-998X, Vol. 110, article id 104406Article in journal (Refereed)
    Abstract [en]

    The Turonian (93.9-89.8 Ma) was a key transitional interval of plesiosaur evolution, during which pliosaurid apex predators (dominant since the Middle Jurassic) rapidly declined, and polycotylids correspondingly radiated as middle trophic-level pursuit hunters. Paradoxically, however, the fossil record of Turonian plesiosaurs is globally sparse, especially in continental Europe where only a handful of fragmentary specimens have been recovered from localities in the Czech Republic, Germany and Poland. Here, we report on a new European Turonian plesiosaur occurrence from the Bochum Grunsand Member of the Duisburg Formation in the city of Unna, western Germany. These remains comprise a series of eight mid-series cervical vertebrae with articulated ribs that can be precisely correlated to the lower middle Turonian UC8a-UC8b calcareous nannofossil biozones. The vertebrae display a distinctive character state combination, including transversely broad lozenge-shaped centra that are anteroposteriorly compact, bear amphicoelous articular surfaces, inset lateral sides, and large zygapophyses that are broader than the corresponding centra. Although phylogenetically inconclusive, these features are compatible with coeval polycotylids. The Bochum Grunsand Member vertebrae thus augment the currently scant knowledge of Turonian plesiosaurs from Europe, and support assertions that the regional assemblage was taxonomically diverse at that time.

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